1. Field of the Invention
Processes and apparatus for treatment of animal manure in agricultural applications.
2. Description of Related Art
The cleanup and handling of dairy cattle, beef cattle, swine, and poultry manure has become a crucial issue in the management of watersheds throughout the United States. There has been increasing publicity and stricter environmental requirements and enforcement regarding this issue, exemplified by the continuing concern over the battle to maintain water quality in areas such as the Chesapeake Bay, New York watersheds, and now sections of the Gulf or Mexico. Major catastrophic releases of manure as well as perpetual normal operational discharges of manure into sensitive watersheds have raised awareness of this issue by the general public.
Processes and chemical treatment regimens for the treatment of animal waste streams are known. For example, U.S. Pat. No. 6,245,121 of Lamy et al., the disclosure of which is incorporated herein by reference, describes a process for the treatment of aqueous effluents containing organic and inorganic matter and having a solids content of at most 12% by weight to provide a purified liquid phase and a solid organic fertilizer or organic soil improver. The process includes subjecting the effluent to one or more primary liquid/solid separation steps to obtain a liquid medium containing no more than 3% by weight of dry matter and having a turbidity of at most 300 NTU and a collection of concentrates containing in total 15% by weight dry matter. The liquid medium is subjected to ultra filtration or micro filtration to obtain an ultra filtrate or a micro filtrate containing at most 1% by weight dry matter and having a turbidity of at most 100 NTU. The ultra filtrate or micro filtrate is subjected to a reverse osmosis operation to obtain a concentrate and a permeate. The permeate constitutes a purified aqueous phase.
United States Patent Application Publication No. US 2003/0057160 of Williams et al., the disclosure of which is incorporated herein by reference, describes an animal waste treatment method comprising flushing animal waste from a barn to a holding tank where the waste is mixed with an alkaline solution to kill pathogens. After neutralization, the solution is separated into solids and liquids. The liquid is treated and recycled as flushing water to clean the barns and/or drinking water for the animals. The solids are separated into digested and undigested feed. The digested feed is further processed for use as a fertilizer and the undigested feed is processed for use as animal feed.
United States Patent Application Publication No. US 2005/0205496 of Pullman et al., the disclosure of which is incorporated herein by reference, discloses a process for treating liquid waste material comprising first adding a chemical flocculent to the liquid waste material followed by mixing to promote flocculation. The floc material is subsequently separated to produce a bulk clarified liquid, with the floc material being subjected to a solids separation to extract further bulk clarified liquid. The collected bulk clarified liquid is then recycled back into at least one of the steps of adding a chemical flocculent and solids separation of the floc material.
Dairy cattle, beef cattle, swine, poultry and other confined animal feeding operations (CAFO's) require significant capital and operating costs for transportation and/or handling, separation and spreading of manure. Current technologies for solids and nutrient separation have inherent limitations, are costly to operate, and result in the use of large quantities of fuel and labor in order to provide solid effluents that can either be recycled or are environmentally acceptable to spread on farmlands, and water-based effluents that are either useful in irrigation, in livestock operations, or as potable water, or are environmentally acceptable to spread on farmlands.
What is needed is a process for treating animal waste that is low in capital equipment cost, low in waste transportation cost, simple to operate, and that provides solid and liquid effluents with the above attributes.